Narrow down your champion pool; pick like 1-2 champions per role to play over like, 2-3 roles (maybe have one or two easy champions in the other roles in case you have to fill) gravitate towards the simpler champions. I'd tell you to stop playing Azir but I'm not sure you'd listen to me, lol. Think of it this way; if you think you have mechanics that are good enough to play Azir (imo the most complicated champion in the game), if you play easier champions, you can just style all over everyone in the game. It might take longer to get good at a new champion, and that's fine, but it will be better for you in the long run; learning your fundamentals will get you farther in this game than any OP FOTM pick. You seem to be having some success with Xerath; I personally think he's too complicated (his ult primarily), but if you're feeling good on him, ride that out.
Resist dying, focus on objectives; KDA doesn't matter. Own up to your mistakes, look to be learning from what you did wrong in a game (everyone makes mistakes) and work to improve your game. Don't worry about your team; it doesn't matter. At this division you can seriously solo carry from any role so long as your teammates are remotely competent (and if you happen to get matched with a particularly bad team, don't sweat it, happens to everyone, law of averages or something). Here's an example from two ranked games I played today:
Here's the first game, I was playing support. I got my ADC fed; super, super fed (she was like 10/0 and 50 CS ahead at one point). And then I threw the game. I tilted super hard, I started dying unnecessarily trying to make plays or whatever, and we lost the game. Sure I can blame my teammates, the Yi who openly admitted they didn't know what they were doing, or the Syndra who didn't look like she understood how her stun worked, but it doesn't change the fact that I made mistakes in that game that, if I played better, I could have single-handedly carried the game, even as Janna support. The important thing is not to dwell on whatever teammates you had since hey, maybe they were having a bad day, maybe it was their first time playing that champion, who really cares since you'll probably never run into them again in solo-q. Focus on correcting your mistakes and improving your own game. I know a lot of mistakes I made that game, and I know I made mistakes that I don't even realize I made, and for me it's about improving off of those so the next time I'm in this situation (which, it's solo-q, will happen again), I will make fewer and fewer mistakes until I can actually carry the game.
Here's the second game. At this point, since I was just coming off that last game, I was sort of in damage-control mode, trying to get myself off tilt. I didn't do much this game, but hey, some games you get lucky and don't have to. From the outside it looks kind of like a stomp, which it was to a degree, but that doesn't mean there's nothing to learn though. I was farming like absolute crap this game, I misplayed most of my fights, my build made no sense whatsoever. What I didn't do, and improved on in this game, was try to make some crazy plays and end up getting myself killed. I toned most things down, maybe to a fault (again, damage-control mode), but I didn't die, I caught up in CS, I let Graves and Leona have a freaking party however they wanted since if I'm not carrying the game, the last thing I should do is become a liability to my team.
It's kind of this weird art of playing to your team while ignoring them at the same time. The first game I kept wanting to get Yi into the fight and start wrecking people, but I wasn't paying attention to the fact that 1. they have an engage comp, I'm a disengage champion, and I can win a fight by just waiting for them to go ham and then disrupting everything they do instead of trying to engage on them, and 2. Yi was second guessing himself, and it would have been better to peel for him and create openings for him to do what Yi does instead of trying to throw him into a fight. In the second game, even with the mistakes I was making, I saw that Graves and Leona were in a position to just face stomp the entire game, so I upgraded my trinket earl(ier), started warding for my team, went around managing side lanes and just let my team do whatever they wanted. Yea I could have carried; the last kill of the game is actually me 100-0 Kassadin right before the surrender vote happened, but it's easier to actually throw the game if I let my ego get in the way, trying to be some superstar that makes all the plays and hogs the ball from my team, instead of focusing on the larger game that's being played.
EDIT: One more tip; check the score board more often, and take it into account when you're playing the game; this is something I rarely do and seriously need to.
